U.S. patent number 5,057,476 [Application Number 07/570,669] was granted by the patent office on 1991-10-15 for platinum catalyst composition, method for its preparation and curable organopolysiloxane compositions containing same.
This patent grant is currently assigned to Dow Corning Toray Silicone Company, Ltd.. Invention is credited to Toshio Saruyama, Hideko Takeda, Atshushi Togashi.
United States Patent |
5,057,476 |
Saruyama , et al. |
October 15, 1991 |
Platinum catalyst composition, method for its preparation and
curable organopolysiloxane compositions containing same
Abstract
A platinum catalyst composition having improved thermal
stability, and all of the utilities of platinum catalyst
compositions of trhe art, is provided by mixing certain
organosiloxanes which contain aryl and alkenyl groups, such as
1,3-divinyl-1,3-diphenyldimethyldisiloxane, in a quantity of at
least 2 moles, with a platinum complex having as a ligand an
organosiloxane which contains alkyl and alkenyl groups, such as
1,3-divinyltetramethyldisiloxane (or a mixture of said platinum
complex and said organosiloxane), in a quantity of 1 mole of
platinum atoms. In a preferred embodiment the mixture is distilled
in vacuo to remove part or all of the organosiloxane which contains
alkyl and alkenyl groups, and most preferably to remove at least a
portion of the complexed organosiloxane which contains alkyl and
alkenyl groups.
Inventors: |
Saruyama; Toshio (Sakura,
JP), Takeda; Hideko (Funabashi, JP),
Togashi; Atshushi (Ichihara, JP) |
Assignee: |
Dow Corning Toray Silicone Company,
Ltd. (Tokyo, JP)
|
Family
ID: |
16826029 |
Appl.
No.: |
07/570,669 |
Filed: |
August 22, 1990 |
Foreign Application Priority Data
|
|
|
|
|
Aug 31, 1989 [JP] |
|
|
1-225230 |
|
Current U.S.
Class: |
502/158; 502/152;
502/169 |
Current CPC
Class: |
C08L
83/04 (20130101); C08G 77/398 (20130101); B01J
31/1675 (20130101); B01J 31/2291 (20130101); C07F
15/0086 (20130101); C08L 83/04 (20130101); C08L
83/00 (20130101); C08L 2666/52 (20130101); C08G
77/08 (20130101); B01J 2231/323 (20130101); C08G
77/12 (20130101); C08G 77/20 (20130101); B01J
2531/828 (20130101); C08G 77/70 (20130101) |
Current International
Class: |
C08G
77/00 (20060101); C08G 77/398 (20060101); C08L
83/00 (20060101); C08L 83/04 (20060101); C07F
15/00 (20060101); B01J 31/16 (20060101); B01J
31/22 (20060101); B01J 031/28 () |
Field of
Search: |
;502/152,158,169 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Garvin; Patrick P.
Assistant Examiner: Peebles; Brent M.
Attorney, Agent or Firm: Grindahl; George A.
Claims
That which is claimed is:
1. A platinum catalyst composition comprising
(A) a platinum complex having as a ligand an organosiloxane which
has no more than 8 silicon atoms in each molecule and contains
alkyl and alkenyl groups and which has in each molecule at least
one bond as represented by the formula ##STR5## wherein R.sup.1 is
an alkyl group having no more than 6 carbon atoms and R.sup.2 is an
alkenyl group, or a mixture of said platinum complex and said
organosiloxane; and
(B) an organosiloxane which contains aryl and alkenyl groups and
has no more than 8 silicon atoms in each molecule and which
contains in each molecule at least one bond as represented by the
formula ##STR6## wherein R.sup.3 is an aryl group and R.sup.2 is
defined as above, in a quantity of at least 2 moles of component
(B) per 1 mole platinum atoms in component (A).
2. A platinum catalyst in accordance with claim 1 in which the
organopolysiloxane of component (A) is
1,3-divinyltetramethyldisiloxane and component (B) is
1,3-divinyl-1,3-diphenyldimethyldisiloxane.
3. A platinum catalyst in accordance with claim 1 further
comprising a platinum complex having as a ligand an organosiloxane
which has no more than 8 silicon atoms in each molecule and
contains aryl and alkenyl groups and which contains in each
molecule at least one bond as represented by the formula ##STR7##
wherein R.sup.3 is an aryl group and R.sup.2 is an alkenyl
group.
4. A platinum catalyst in accordance with claim 3 in which the
organopolysiloxane of component (A) is
1,3-divinyltetramethyldisiloxane and the organosiloxane ligand
which has no more than 8 silicon atoms in each molecule and
contains aryl and alkenyl groups and which contains in each
molecule at least one bond as represented by the formula ##STR8##
wherein R.sup.3 is an aryl group and R.sup.2 is an alkenyl group is
1,3-divinyl-1,3-diphenyldimethyldisiloxane.
5. A platinum catalyst in accordance with claim 4 which is free of
uncomplexed divinyltetramethyldisiloxane.
6. A method for the preparation of a platinum catalyst composition,
said method comprising mixing
(A) a platinum complex having as a ligand an organosiloxane which
has no more than 8 silicon atoms in each molecule and contains
alkyl and alkenyl groups and which has in each molecule at least
one bond as represented by the formula ##STR9## wherein R.sup.1 is
an alkyl group having no more than 6 carbon atoms and R.sup.2 is an
alkenyl group, or a mixture of said platinum complex and said
organosiloxane; and
(B) an organosiloxane which contains aryl and alkenyl groups and
has no more than 8 silicon atoms in each molecule and which
contains in each molecule at least one bond as represented by the
formula ##STR10## wherein R.sup.3 is an aryl group and R.sup.2 is
defined as above, in a quantity of at least 2 moles of component
(B) per 1 mole platinum atoms in component (A).
7. A method in accordance with claim 6 in which the
organopolysiloxane of component (A) is
1,3-divinyltetramethyldisiloxane and component (B) is
1,3-divinyl-1,3-diphenyldimethyldisiloxane.
8. A method in accordance with claim 6 further comprising removing
at least a portion of the organosiloxane in component (A) by
distillation in vacuo.
9. A method in accordance with claim 8 in which the
organopolysiloxane of component (A) is
1,3-divinyltetramethyldisiloxane and component (B) is
1,3-divinyl-1,3-diphenyldimethyldisiloxane.
10. A method in accordance with claim 9 wherein at least a portion
of the complexed divinyltetramethyldisiloxane is removed.
11. The platinum catalyst composition obtained by the method of
claim 6.
12. The platinum catalyst composition obtained by the method of
claim 7.
13. The platinum catalyst composition obtained by the method of
claim 8.
14. The platinum catalyst composition obtained by the method of
claim 9.
15. The platinum catalyst composition obtained by the method of
claim 10.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a platinum catalyst composition
which may be used as a catalyst, inter alia, of the hydrosilylation
reaction, to a method for its preparation, and to a curable
organopolysiloxane composition which contains said platinum
catalyst composition.
A large number of platinum compounds are known as hydrosilylation
reaction catalysts. Among these, the platinum/alkenylsiloxane
complex catalyst compositions as disclosed in Japanese Patent
Publication Number 42-22924 (22,924/67) and Japanese Patent
Publication Number 46-28795 (28,795/71) have a high catalytic
activity and are useful as hydrosilylation reaction catalysts.
These are prepared by a reaction, for example, between alkenyl
group-containing siloxane and chloroplatinic acid.
However, this type of platinum catalyst composition generally
suffers from a poor storage stability, and, unless careful
attention is paid to its method of storage, it readily deteriorates
into platinum black with a concomitant substantial loss in
catalytic activity. For example, the catalyst suffers from a loss
in activity within a few hours merely upon an increase in storage
temperature. Moreover, its storage stability is also sharply
reduced by other substances which may be compounded into the
reaction system.
A large number of methods have been introduced in order to solve
these problems. For example, Japanese Patent Publication Number
47-23679 (23,679/72) proposes that the storage stability be
increased by removing the halide in the prepared
platinum/alkenylsiloxane complex catalyst composition. In this
method, the platinum/alkenylsiloxane complex catalyst composition
is stored as such or in a neutral medium such as polysiloxane, and
this represents an effective approach as long as the catalyst
composition is placed in an environment free of temperature
increases. However, this method is unsatisfactory with regard to
the storage stability in the presence of non-neutral substances or
in an environment suffering from temperature increases.
Japanese Patent Publication Numbers 46-28795 (28,795/71) and
46-29731 (29,731/71) disclose a platinum/alkenylsiloxane complex
catalyst composition which is prepared using phenyl
group-containing alkenylsiloxane. However, one encounters very low
platinum-based yields in the preparation by conventional methods of
platinum complex catalyst compositions having these
phenyl-containing alkenylsiloxane ligands, and the problem then
arises of poor economics.
In addition, Japanese Patent Application Laid Open (Kokai) Number
56-136655 (136,655/81) proposes a method for the preparation of a
platinum/alkenylsiloxane complex catalyst composition via the
bis-(1,5-cyclooctadiene)/Pt complex by ligand exchange with
siloxane which contains the alkyl and alkenyl groups. Again, the
economics of this method are poor due to the low yield of the
intermediate bis-(1,5-cyclooctadiene)/Ft complex and due to the
reduction in yield arising from the rapid decomposition to platinum
black when this intermediate's solution comes into contact with the
air.
Thus, as discussed above, there have already been various attempts
at improving the storage stability of Pt/alkenylsiloxane complex
catalyst compositions. Nevertheless, aside from storage in a
neutral medium in a low temperature ambient, no Pt/alkenylsiloxane
complex catalyst composition has been discovered which evidences an
excellent storage stability as well as good economics, nor has a
method for the preparation of same been discovered.
BRIEF SUMMARY OF THE INVENTION
The present inventors achieved the present invention as the result
of extensive investigations directed at solving the aforementioned
problems.
A platinum catalyst composition having improved thermal stability
is provided by mixing certain organosiloxanes which contain aryl
and alkenyl groups, in a quantity of at least 2 moles, with a
platinum complex having as a ligand an organosiloxane which
contains alkyl and alkenyl groups, or a mixture of said platinum
complex and said organosiloxane, in a quantity of 1 mole of
platinum atoms.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a platinum catalyst composition
composed of (A) a platinum complex having as a ligand an
organosiloxane which has no more than 8 silicon atoms in each
molecule and contains alkyl and alkenyl groups and which has in
each molecule at least one bond as represented by the following
formula ##STR1## wherein R.sup.1 is an alkyl group having no more
than 6 carbon atoms and R.sup.2 is an alkenyl group, or a mixture
of said platinum complex and said organosiloxane; and (B) an
organosiloxane which contains aryl and alkenyl groups and has no
more than 8 silicon atoms in each molecule and which contains in
each molecule at least one bond as represented by the following
formula ##STR2## wherein R.sup.3 is an aryl group and R.sub.2 is
defined as above, in a quantity of at least 2 moles of component
(B) per 1 mole platinum atoms in component (A).
To explain this in greater detail, component (A) comprises a
platinum complex having as ligand an organosiloxane which has no
more than 8 silicon atoms in each molecule and contains alkyl and
alkenyl groups and which has in each molecule at least one bond as
represented by the following formula. ##STR3##
In the preceding formula R.sup.1 is an alkyl group having no more
than 6 carbon atoms such as methyl, ethyl, propyl, etc., and
R.sup.2 is an alkenyl group such as vinyl, allyl, etc.
Component (A) can also be the mixture of said platinum complex and
said organosiloxane.
This component (A) may consist simply of the aforementioned
platinum complex, but it may also be a mixture of said platinum
complex with organosiloxane identical to or of the same type as the
(alkyl+alkenyl)-containing organosiloxane coordinated in said
platinum complex. (Alkyl +alkenyl)-containing organosiloxane not
coordinated within the platinum complex should be present as a
general matter at no more than 30 moles per 1 mole platinum atoms
in the platinum complex.
This component (A) is in fact known, for example, as disclosed in
Japanese Patent Publication Number 42-22924. In general, it is
prepared by reacting, with heating, (alkyl+alkenyl)-containing
siloxane with haloplatinic acid or haloplatinic acid salt. In the
preparation of component (A) by this method, the alkenyl group in
the starting (alkyl+alkenyl)-containing siloxane is generally the
vinyl group. Moreover, it is preferred that the alkyl group be the
methyl group considering the economics and prevention of side
reactions during preparation of the platinum complex comprising
component (A). Although no specific restriction is placed on groups
which may be present in addition to the alkenyl and alkyl groups,
it is necessary in particular to avoid aryl groups since this
causes a reduction in the platinum yield in the preparation of
component (A). Examples of this (alkyl+alkenyl)-containing siloxane
are 1,3-divinyltetramethyldisiloxane and
1,3,5,7-tetravinyltetramethylcyclotetrasiloxane.
The (aryl+alkenyl)-containing siloxane comprising component (B) is
the crucial component for increasing the stability of the platinum
complex comprising component (A). In order to increase the
stability of the platinum catalyst, this siloxane must contain no
more than 8 silicon atoms in each molecule and must contain in each
molecule at least one bond as represented by the next formula.
##STR4##
In the preceding formula R.sup.3 is an aryl group such as phenyl,
etc., and R.sup.2 is an alkeny1 group such as vinyl, allyl, etc.
Such (aryl+alkenyl)-containing siloxanes are exemplified by
1,3-divinyl-1,3-diphenyldimethyldisiloxane and
1,3-divinyltetraphenyldisiloxane.
Component (B) must be added in a quantity of at least 2 moles per 1
mole platinum atoms in component (A), and a stabilizing effect on
the platinum catalyst comprising component (A) cannot be obtained
at less than 2 moles.
The platinum catalyst composition of the present invention may be
prepared by the method of this invention which comprises mixing the
aforesaid components (A) and (B), in the amounts stated, and,
optionally, then removing a portion of the
(alky+alkenyl)-containing siloxane in component (A) by distillation
in vacuo.
While the platinum catalyst composition of the present invention
may be prepared according to either of these methods, preparation
according to the latter method is preferred because it affords a
more storage-stable platinum catalyst composition.
Thus, according to the latter method, a platinum catalyst
composition with an even more superior storage stability is
prepared by removal of part of the platinum-coordinated
(alkyl+alkenyl)-containing organosiloxane and part or all of the
non-platinum-coordinated (alkyl+alkenyl)-containing organosiloxane
in component (A) and substitution with the
(phenyl+alkenyl)-containing organosiloxane of component (B).
The platinum catalyst composition of the present invention has the
same catalytic activity as prior platinum/siloxane complexes.
However, the platinum catalyst composition of the present invention
is distinguished by a better high-temperature stability and a
better stability against other substances present in the system
than the platinum/siloxane complexes known from the art.
Exploiting these distinguishing features, it can be used as a
hydrosilylation reaction catalyst in the synthesis of silanes and
siloxanes and also as a curing catalyst for those well-known
organopolysiloxane compositions which cure by the hydrosilylation
reaction.
Thus, the present invention further comprises a curable
organopolysiloxane composition comprising the admixture of the
platinum catalyst composition of this invention, at 0.1 to 100
parts by weight of platinum atoms, with a million parts by weight
of a mixture of an organopolysiloxane having at least 2 alkenyl
groups in each molecule and organohydrogenpolysiloxane having at
least 2 silicon-bonded hydrogen atoms in each molecule.
The organopolysiloxane having at least 2 alkenyl groups in each
molecule and the organohydrogenpolysiloxane having at least 2
silicon-bonded hydrogen atoms in each molecule can be any that are
well-known in the organosilicon art.
The present invention is explained below by illustrative examples,
in which parts is weight parts in all cases and the % platinum
content refers to a weight %.
EXAMPLE 1
200 Grams chloroplatinic acid (platinum content=40%), 400 g
1,3-divinyltetramethyldisiloxane, 400 g sodium bicarbonate, and
1,000 g isopropyl alcohol were mixed and reacted with heating at 70
to 80 degrees Centigrade for 30 minutes. After removal of the
produced salt by filtration, the isopropyl alcohol was removed in
vacuo at 50 degrees Centigrade, and, after cooling, the
precipitated salt was filtered off a second time. This afforded
platinum catalyst composition A comprising
1,3-divinyltetramethyldisiloxane and a platinum complex having
1,3-divinyltetramethyldisiloxane as ligand. Its platinum content
was 5.4%, and the platinum yield was 97.5%.
36 Grams 1,3-divinyl-1,3-diphenyldimethyldisiloxane was added and
mixed into 100 g platinum catalyst composition A, and platinum
catalyst composition B was then obtained by conducting distillation
in vacuo at 0.03 torr and 50 degrees Centigrade to remove the
1,3-divinyltetramethyldisiloxane. Its platinum content was 8.8%,
and the platinum yield from platinum catalyst composition A was
99.2%. These platinum catalyst compositions were analyzed by
nuclear magnetic resonance spectral analysis (NMR). Only a single
peak at 6133 ppm was observed from platinum catalyst composition A
by .sup.195 Pt-NMR. On the other hand, in addition to the peak at
6133 ppm observed for platinum catalyst composition A, platinum
catalyst composition B gave a multiplet peak extending over -6080
to -6128 ppm, and the molar ratio between the two was 19%/81%.
These results indicated that over 80% of the platinum in platinum
catalyst composition B had been converted into a new complex from
the platinum complex in platinum catalyst composition A.
Platinum catalyst compositions A and B obtained as above were both
diluted to a 2% platinum content by vinyl-terminated
polydimethylsiloxane, and the decomposition temperature of the
catalyst (temperature at which the transparent solution converted
to brown) was measured at a temperature-rise rate of 1 degree
Centigrade/minute.
Platinum catalyst composition A and platinum catalyst composition B
were also respectively added at 1 ppm (platinum weight) to
equimolar pentamethyldisiloxane and 3-vinylheptamethyltrisiloxane.
The reaction rates at 25 degrees Centigrade of the obtained
siloxane compositions were measured by means of gas chromatography,
and these results are reported in Table 1.
As these results make clear, platinum catalyst composition B, which
was prepared in accordance with the present invention, was more
stable than platinum catalyst composition A while at the same time
its catalytic activity remained unchanged.
TABLE 1 ______________________________________ present invention
comparison example platinum catalyst platinum catalyst composition
B composition A ______________________________________
decomposition 138.degree. C. 85.degree. C. temperature catalytic
activity 25 minutes 25 minutes (half-life)
______________________________________
COMPARATIVE EXAMPLE 1
Proceeding as for the synthesis of platinum catalyst composition A
in Example 1, a platinum complex was prepared as in Example 1, but
using 400 g 1,3-divinyltetramethyldisiloxane and 100 g
1,3-divinyl-1,3-diphenyldimethyldisiloxane in place of the 400 g
1,3-divinyltetramethyldisiloxane. However, the reaction rate was
very slow, and platinum complex was not obtained by reaction for 30
minutes at 70 to 80 degrees Centigrade. The platinum yield did not
exceed a maximum of 56% during reaction with heating for 60
minutes. When the heated reaction was conducted for longer periods
of time, the platinum yield after final filtration fell off due to
an increase in platinum black production, and it declined to 35%
after 120 minutes.
Moreover, when a platinum catalyst composition was prepared as in
Example 1 by replacing the 1,3-divinyltetramethyldisiloxane in
Example 1 with 1,3-divinyl1,3-diphenyldimethyldisiloxane, the
reaction rate was even slower and the maximum platinum yield was
also reduced.
The preceding makes clear that the platinum yield is sharply
reduced when a (phenyl+vinyl)-containing organosiloxane is
simultaneously present in the synthesis of the alkenyl/Pt
complex.
EXAMPLE 2
Platinum catalyst composition B as obtained in Example 1 was mixed
to give 5 ppm as the weight of platinum into 100 parts
vinyl-terminated dimethylpolysiloxane (viscosity=12,000
centistokes) to prepare a mixture. Curable organopolysiloxane
compositions were obtained by the addition to such a mixture,
either immediately after mixing or after its ageing for 2 weeks at
70 degrees Centigrade, of 0.9 parts methylhydrogenpolysiloxane with
the average structural formula
and 0.02 parts methylbutynol. The curing performance was then
measured as the gelation time at 130 degrees Centigrade, and these
measurement results are reported in Table 2. For comparison,
curable organopolysiloxane compositions were prepared as above, but
using platinum catalyst composition A in place of platinum catalyst
composition B. The curing performance of these compositions was
also measured as above, and these results again are reported in
Table 2.
These measurement results make it clear that the platinum catalyst
composition of the present invention has a high storage
stability.
TABLE 2 ______________________________________ present invention
comparison example ______________________________________
immediately after 30 seconds 29 seconds mixing after ageing 29
seconds 97 seconds ______________________________________
EXAMPLE 3
A platinum catalyst composition C was prepared by the addition with
mixing to homogeneity of 3.0 g
1,3-divinyl-1,3-diphenyldimethyldisiloxane to 10 g platinum
catalyst composition A as prepared in Example 1.
Using this platinum catalyst composition C in place of the platinum
catalyst composition B used in Example 2, a curable
organopolysiloxane composition was then prepared proceeding
otherwise the same as in Example 2.
The curing performance of this composition was measured as in
Example 2: the gelation time at 130 degrees Centigrade was 33
seconds for the curable organopolysiloxane composition which used
the platinum catalyst composition immediately after mixing, while
the gelation time at 130 degrees Centigrade was 31 seconds for the
curable organopolysiloxane composition which used the aged platinum
catalyst composition.
EFFECTS OF THE INVENTION
As discussed above, because the platinum catalyst composition of
the present invention consists of component (A) and component (B),
it is distinguished by an excellent storage stability. Moreover,
the preparative method of the present invention is distinguished by
the inexpensive and highly productive preparation of the platinum
catalyst composition under consideration.
Furthermore, the curable organopolysiloxane composition which
contains said platinum catalyst composition is itself distinguished
by an excellent storage stability.
* * * * *